Project description:The endothelium first forms in the blood islands in the extra-embryonic yolk sac and then throughout the embryo to establish circulatory networks that further acquire organ-specific properties during development to support diverse organ functions. Here, we investigated the properties of endothelial cells (ECs), isolated from four human major organsthe heart, lung, liver, and kidneys in individual fetal tissues at three months' gestation, at gene expression, and at cellular function levels. We showed that organ-specific ECs have distinct expression patterns of gene clusters, which support their specific organ development and functions. These ECs displayed distinct barrier properties, angiogenic potential, and metabolic rate and support specific organ functions. Our findings showed the link between human EC heterogeneity and organ development and can be exploited therapeutically to contribute in organ regeneration, disease modeling, as well as guiding differentiation of tissue-specific ECs from human pluripotent stem cells.
Project description:Each organ of the human body requires locally-adapted blood vessels1–3. The gain of such organotypic vessel specializations is often deemed molecularly unrelated to the process of organ vascularization. Opposing this model, we reveal a molecular mechanism for brain-specific angiogenesis that operates under the control of Wnt7a/b ligands, well-known blood-brain barrier maturation signals4–6. The control mechanism relies on Wnt7a/b-dependent expression of Mmp25 in brain endothelial cells. This hitherto poorly characterized GPI-anchored matrix metalloproteinase is selectively required in endothelial tip cells to enable their initial migration across the pial basement membrane which lines the brain surface, and whose distinctive molecular composition is controlled by embryonic pial fibroblasts. Mechanistically, Mmp25 confers brain invasive competence by cleaving the pial basement membrane-enriched Col4a5/6 within a short non-collagenous region of the central helical part of the heterotrimer. Upon genetic interference with pial basement membrane composition, the Wnt/β-catenin-dependent organotypic control of brain angiogenesis is lost, resulting in a properly patterned, yet blood-brain barrier-defective cerebrovasculature. This work reveals an organ-specific angiogenesis mechanism, sheds light on tip cell mechanistic angiodiversity, and thereby illustrates how organs, by imposing local constraints on angiogenic tip cells, can select vessels matching their distinctive physiological requirements.
Project description:The goal of this study was to gain insight into the molecular heterogeneity of capillary endothelial cells derived from different organs by microarray profiling of freshly isolated cells and identify transcription factors that may determine the specific gene expression profile of endothelial cells from different tissues. The study focused on heart endothelial cells and presents a validated signature of 31 genes that are highly enriched in heart endothelial cells. Within this signature 5 transcription factors were identified and the optimal combination of these transcription factors was determined for specification of the heart endothelial fingerprint. From three tissue types (mouse brain, heart and liver), we collected five freshly isolated endothelial cell samples each. For each brain sample we pooled RNA from 6 mice. For each heart sample we pooled RNA from 4 mice. For each liver sample we pooled RNA from 2 mice. The three endothelial subtypes were then compared. For each subtype, specific gene profiles were defined by determining the genes that were highly enriched versus the other two endothelial subtypes.
Project description:Each organ of the human body requires locally-adapted blood vessels. The gain of such organotypic vessel specializations is often deemed molecularly unrelated to the process of organ vascularization. Opposing this model, we reveal a molecular mechanism for brain-specific angiogenesis, that operates under the control of Wnt7a/b ligands, well-known blood-brain barrier maturation signals. The control mechanism relies on Wnt7a/b-dependent expression of Mmp25 in brain endothelial cells. This hitherto poorly characterized GPI-anchored matrix metalloproteinase is selectively required in endothelial tip cells to enable their initial migration across the pial basement membrane lining the brain surface, which distinctive molecular composition is controlled by embryonic pial fibroblasts. Mechanistically, Mmp25 confers brain invasive competence by cleaving the pial basement membrane-enriched Col4a5/6 within a short non-collagenous region of the central helical part of the heterotrimer. Upon genetic interference with pial basement membrane composition, the Wnt/β-catenin-dependent organotypic control of brain angiogenesis is lost, resulting in properly patterned, yet blood-brain barrier-defective cerebrovasculatures. This work reveals an organ-specific angiogenesis mechanism, sheds light on tip cell mechanistic angiodiversity, and thereby illustrates how organs, by imposing local constraints on angiogenic tip cells, can select vessels matching their distinctive physiological requirements.
Project description:The goal of this study was to gain insight into the molecular heterogeneity of capillary endothelial cells derived from different organs by microarray profiling of freshly isolated cells and identify transcription factors that may determine the specific gene expression profile of endothelial cells from different tissues. The study focused on heart endothelial cells and presents a validated signature of 31 genes that are highly enriched in heart endothelial cells. Within this signature 5 transcription factors were identified and the optimal combination of these transcription factors was determined for specification of the heart endothelial fingerprint.
Project description:Microvascular endothelial cells (EC) are increasingly recognized as organ-specific gatekeepers of their microenvironment. Microvascular EC instruct neighboring cells in their organ-specific vascular niches by angiocrine factors that comprise secreted growth factors/angiokines, but also extracellular matrix molecules and transmembrane proteins. The molecular regulators, however, that drive organ-specific microvascular transcriptional programs and thereby regulate angiodiversity, are largely elusive. Opposite to continuous barrier-forming EC, liver sinusoids are a prime model of discontinuous, permeable micro-vessels. Here, we show that transcription factor GATA4 controls liver sinusoidal endothelial (LSEC) specification and function. LSEC-restricted deletion of GATA4 caused transformation of discontinuous liver sinusoids into continuous capillaries. Capillarization was characterized by ectopic basement membrane deposition and formation of an abundantly VE-Cadherin expressing continuous endothelium. Correspondingly, ectopic expression of GATA4 in cultured continuous EC mediated downregulation of continuous EC transcripts and upregulation of LSEC genes. Regarding angiocrine functions, the switch from discontinuous LSEC to continuous EC during embryogenesis caused liver hypoplasia, fibrosis, and impaired colonization by hematopoietic progenitor cells resulting in anemia and embryonic lethality. Thus, GATA4 acts as master regulator of hepatic microvascular specification and acquisition of organ-specific vascular competence indispensable for liver development. The data also establish an essential role of the hepatic microvasculature for embryonic hematopoiesis.